Each day, large quantities of freight which has a cumulative value of many millions of dollars are shipped throughout the United States and throughout the world. For example, large quantities of freight are loaded into rail cars and shipped by railroad. Likewise, large quantities of freight are stored in shipping containers and shipped by ship or barge. Even larger quantities of freight, however, is commonly loaded into trailers and shipped by truck.
Due to the quantity and the value of the freight, the owner of the freight as well as the shipper who has assumed custodial responsibility for the freight would like to track the position or location of the freight, regardless of its mode of transportation. Moreover, the owner of the freight as well as the shipper would oftentimes also like to monitor the status of the freight while the freight is in route. For example, it may be desirable to monitor the temperature of a refrigerated trailer in transport to insure that the refrigerated products stored within the trailer are appropriately chilled.
Accordingly, a variety of tracking systems have been developed which are designed to track the location and, in some instances, the status of freight during shipment. With respect to the trucking industry, however, these tracking systems typically track the location of the truck or tractor, and fail to track the location of the trailer, especially in instances in which the trailer is no longer attached to a tractor. In particular, conventional tracking systems are designed to track the location of the tractor since the tractor is generally worth many times more than an empty trailer.
For example, the earliest method of tracking the progress of a tractor-trailer required the driver to periodically park the tractor and to telephone the central station or dispatcher in order to report the present location of the tractor-trailer and to obtain updated delivery information. By requiring the driver to periodically telephone the central station or dispatcher, however, the average speed of the tractor-trailer was significantly reduced. In addition, the information relating to the present location of the tractor-trailer provided by the drivers was sometimes inaccurate due either to inadvertent mistakes or attempts by the driver to intentionally mislead the dispatcher regarding the progress of the tractor-trailer.
As a result, more sophisticated tracking systems have been developed which allow communications to be established between the driver of a tractor and a central station or dispatcher, while the tractor-trailer continues along its route. These tracking systems can also include a receiver mounted to the tractor for communicating with the Global Positioning System (GPS) satellites in order to determine the present location of the tractor-trailer. The tracking systems can then transmit information relating to the present position of the tractor-trailer to the central station or dispatcher without requiring the driver to stop the tractor-trailer and to telephone the central station or dispatcher.
Conventional tracking systems can also include one or more sensors for monitoring predetermined engine parameters, such as the oil pressure or engine temperature. Data representing these parameters can then be transmitted to the central station or dispatcher on an event-triggered, i.e., emergency, basis, on a regularly scheduled basis or as requested or polled. In addition, conventional tracking systems can include one or more sensors mounted within or upon the trailer in order to monitor predetermined conditions within the trailer, such as the temperature within a refrigerated trailer. In a like fashion, these tractor-based tracking systems can then transmit the sensory signals provided by the trailer sensors to the central station or dispatcher. Accordingly, conventional tracking systems can track the location of the tractor, while monitoring one or more predetermined engine or trailer conditions as the tractor-trailer continues along its route.
As described above, these conventional tractor-based systems can provide information relating to the location of the trailer and the status of the trailer and its contents only so long as the trailer is tethered to the tractor. Once the trailer has been untethered or unhitched from the tractor, however, conventional tracking systems can no longer track the location of the trailer and can no longer monitor the status of the trailer or its contents. Thus, even though conventional tracking systems have historically been thought to be sufficient due to the much greater cost of a tractor than an unloaded trailer, it has recently been observed that the trailer and the contents of the trailer are as valuable, if not more valuable, than the tractor. In addition, it has been found that a shipper can create significant customer distrust and ill-will by failing to adequately track and monitor the location and status of a trailer which contains the customer's freight, even after the trailer has been untethered or unhitched from the tractor. Conversely, substantial customer trust and loyalty could be established by a shipper if the shipper could accurately track and monitor the location and status of the customer's freight throughout the delivery process.
At best, conventional tracking systems may be able to identify the location of the trailer at the time at which the tractor was untethered or unhitched from the trailer. In some instances, however, the driver may neglect to identify or mark the exact location at which the trailer is parked, thereby making it relatively difficult, if not impossible, to locate the trailer. Notwithstanding the capabilities of conventional tracking systems, a trailer would also be difficult, if not impossible, to locate if the trailer were moved after the trailer was untethered from the tractor, such as in instances in which the trailer was stolen or otherwise moved without notifying the shipper or the owner of the freight. Accordingly, even shippers which equip their tractor-trailers with conventional tracking systems may be placed in the unenviable position of attempting to explain to the owner of lost freight why they are unable to locate the trailer in which their freight has been shipped.